CDC laboratory analysis showed that the rabies virus detected in a man who died after an organ transplant was a raccoon type. / 2002 AP photo by Jon Pieree Lasseigne

by Elizabeth Weise, USA TODAY

by Elizabeth Weise, USA TODAY

Health officials confirmed Friday that a Maryland man who received a donated kidney a year and a half ago contracted rabies and died from it.

The discovery was "very surprising," and only the second known time rabies has been transmitted through donated organs in the United States. The finding sent Centers for Disease Control and Prevention (CDC) officers flying to the phones to alert three other people who had received organs from the same donor. All have been treated and remain healthy.

Rabies is extremely rare in the United States: only one to three deaths a year. The fact that it took more than a year for the recipient to begin to show symptoms threw off investigators, as rabies usually develops within a month or two.

"We were all saying, 'Wow, how is this possible?' " said Richard Franka, lead of the rabies team at the CDC in Atlanta.

Here's what happened: In September 2011, a 20-year-old Air Force airman in Pensacola, Fla., died of encephalitis, an inflammation of the brain, said Department of Defense spokeswoman Cynthia Smith. His doctors couldn't find a reason for his illness.

At one point, the doctors thought it might have been some sort of poisoning "because they couldn't come up with a cause. They did a full work-up; they tested for everything they could think of. Even after he died, they sent more tests in and couldn't find a cause," said Matthew Kuehnert, director of the CDC's office of blood, organ and other tissue safety.

The man's family made the decision to donate his kidneys, liver and heart. "Encephalitis wouldn't have excluded him as a donor," said CDC spokeswoman Melissa Dankel. There are many causes of encephalitis, some of which are infectious and some of which aren't. Transplant specialists have a policy for assessing donors who have had encephalitis.

One of the man's kidneys went to a Maryland Army veteran in September 2011. The recipient did fine until last month, when he, too, fell ill with unspecified encephalitis. The Maryland Department of Health and Mental Hygiene started an investigation into the case but couldn't find a cause for his illness. After several weeks doctors started to suspect he perhaps had rabies. Unfortunately, the patient died that same day, before they could begin treatment, Franka said.

Despite the common belief that rabies causes people to act crazy and foam at the mouth, it's actually difficult to diagnose and is easily confused with other pathogens that cause encephalitis, Franka said. CDC laboratory analysis showed that the rabies virus was a raccoon type. In the United States, there's only one recorded case of a person dying from a raccoon-type rabies virus.

Then the question became: How did the Maryland veteran get rabies?

Investigators went over his life with a fine-toothed comb but couldn't find any indication he had been exposed to wildlife. They knew he'd gotten a donated kidney, "but we were thinking it couldn't be the transplant because of the long incubation period," Franka said. "We were wrong."

Each year in the United States, about 28,000 people receive donated organs, said Joel Newman with the United Network for Organ Sharing in Richmond, Va. Only once before in the United States, in 2004, has an infected organ donor passed along rabies to organ recipients, and they all became ill and died very quickly.

Eventually, investigators went back to the Air Force organ donor's medical history. He, too, had no exposure to wildlife. Finally, they discovered that he was originally from North Carolina, but when he joined the Air Force in May 2011, he had first been posted to Texas and then Florida where he was training to be an airplane mechanic. Doctors now believe he was infected either in Texas or North Carolina, though they still don't know how or when.

The definitive laboratory finding that the Maryland man had died of rabies came on March 8. "At that point, we started urgently contacting the patients" who had received the donor's other kidney, liver and heart, Kuehnert said. They lived in Florida, Georgia and Illinois; each was immediately started on anti-rabies shots and remain in good health, he said.

All organ donors go through an intensive screening for diseases that might be transmitted, such as hepatitis, HIV and cytomegalovirus. A detailed medical history is also taken and a physical inspection of the body is done, said Newman.

"Transplant professionals at Walter Reed National Military Medical Center working through the Organ Procurement Network, in conjunction with organ procurement organizations, evaluate donors and take great precautions to avoid disease transmission while understanding that the risk is always present," said Smith, the Defense Department spokeswoman.

Rabies is not tested for because it is very difficult to detect before its victim begins to show symptoms, said the CDC's Kuehnert. The testing can also take weeks. That's impossible in organ donation where the time window is less than 48 hours and for some organs just six hours.

Rabies is a viral disease often transmitted through the bite of a rabid animal. The virus infects the central nervous system, ultimately causing disease in the brain and death within days of the onset of illness if treatment is not begun in time. In the United States, bat bites are the most frequent cause of rabies in humans.